Cardiac Conduction Pathway System - correct answer SA node> AV node> Bundle of His> Left and Right bundle branches> Purkinjie fibers
Pacemakers of the
... [Show More] heart - correct answer ♥ Natural: SA Node = 60-100 beats/minute
♥ Backup: AV Node = 40-60 beats/minute
♥ Backup: Purkinje Fibers (ventricles) = 20-40 beats/minute
SA Node - correct answer • Intrinsic Pacemaker of the heart
• Rate 60-100 beats/min
• RA (Right Atrium), close to SVC (Superior Vena Cava)
• Blood supply from RCA (Right Coronary Artery) & LCA (Left Coronary Artery)
Interatrial/Internodal Tracts - correct answer Transmits impulses from the SA node to the AV node through the RA & LA
AV node - correct answer • Slows conduction (40-60 beats/min)
• Physiologic delay allows atrial kick on floor of RA near tricuspid valve
Bundle of His - correct answer Bundle of cardiac muscle fibers that conducts the electrical impulses from the AV node in the right atrium to the septum between the ventricles and then to the left and right ventricles.
bundle branches - correct answer Right and Left (Left anterior & Left posterior fascicles)
Purkinjie Fibers - correct answer Fibers from Bundle Branches imbedded into the ventricle walls.
Depolarization vs Repolarization - correct answer Depolarization - electrical excitation of the cell membrane, normally followed by mechanical contraction
Repolarization - return of cell membrane to its resting state, normally followed by mechanical relaxation
Electrical and mechanical activity of the heart - correct answer ♥ The heart has two activities that are performed rhythmically: electrical activity followed by mechanical activity
♥ Electrical activity always precedes mechanical activity
♥ It is possible to have electrical activity without mechanical response
♥ Always check the patient - Do Not Depend on the Machine!!!
Measurement of the boxes in the ekg - correct answer ♥ A standard ECG is printed at 25mm per second or 25 small squares per second. Since one second divided by 25 small boxes, then each 1 mm box = 0.04 seconds. The larger boxes indicated by the heavier lines are equal to 0.20 seconds.
♥ Voltage is measured along the vertical axis and is expressed in millivolts (mV). The standard calibration is that a 1 mV signal produces a 10-mm deflection (0.1 mV=1mm). Simply put 10 small squares vertically is equal to 1 millivolt
EKG waveforms and intervals - correct answer ♥ P wave - rounded with upright deflection in lead II, atrial depolarization
♥ PR interval- delay @ AV junction
• measure from beginning of P wave to beginning of QRS
• Normal duration 0.12 - 0.20 seconds •
S wave - Negative deflection following the R-wave
♥ QRS complex - multiple components, Ventricular depolarization, - 0.06 -0.11
• Q wave - first negative deflection after P wave R wave
• Positive deflection after the Q
♥ J point - marks where the QRS complex ends and the ST segment begins [Show Less]